I suspect that the basis of our notion of cuteness is things that evoke our instinctive protective response to infants. Cute things have infantile proportions: think of the disproportionately large eyes and paws of a puppy. Man-made artifacts are seen as cute if they have analogous proportions. Witness: the cutest domestic U-boat is the U18B: perceptibly smaller (shorter) than other GE road locomotive (perceptibly, that is, to those who have some familiarity with what a GE diesel locomotive looks like), but with standardized cab, etc, that seem oversize.

Northwest-- Suspect you are right. Identified as U6B on the Fallen Flags site index. (There are a bunch of photos of units of this class, some of them showing the track they are on: perspective makes it hard to judge, but in at least some of the photos it looked as if they were on track narrower than South African railways' "standard" gauge of 3 foot 6 inches.)

The trucks look like those I have seen in pictures of the 2 foot gauge units: the traction motors are evidently too large to fit entirely inside the truck frames, so you can see their ends sticking out at the sides.

So, maybe if MEC407's mom relents and lets him have one, he can take it for walks at one of the Maine narrow gauge museums with 2 foot gauge track. (Grin! … I sometimes fantasize about alternative history scenarios that would have allowed one or more of the Maine 2 foot gauge railroads to survive long enough to buy some of these.)